CVE-2018-13655 in GFC
Summary
by MITRE
The mintToken function of a smart contract implementation for GFC, an Ethereum token, has an integer overflow that allows the owner of the contract to set the balance of an arbitrary user to any value.
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Analysis
by VulDB Data Team • 02/28/2020
The vulnerability identified as CVE-2018-13655 represents a critical integer overflow flaw within the mintToken function of a smart contract implementation for the GFC Ethereum token. This vulnerability resides in the fundamental arithmetic operations of the contract code, where insufficient input validation and overflow protection mechanisms allow malicious actors to manipulate token balances. The integer overflow occurs when the contract attempts to increment token balances beyond the maximum value that can be represented by the underlying data type, creating a scenario where the balance wraps around to zero or negative values. This flaw directly violates the core principles of secure smart contract development and demonstrates a failure in proper boundary checking and overflow prevention measures that are essential for maintaining the integrity of digital asset systems. The vulnerability is particularly dangerous because it grants the contract owner unprecedented control over user balances, effectively allowing them to manipulate the token economy in ways that could destabilize the entire system.
The technical implementation of this vulnerability stems from the absence of proper overflow checks in the mintToken function, which is typically designed to create new tokens and allocate them to user accounts. When the function processes token minting operations, it performs arithmetic calculations without validating whether the resulting values would exceed the maximum limits of the data type being used. This creates a condition where an attacker can manipulate the input parameters to cause the arithmetic operation to overflow, resulting in unintended balance modifications. The vulnerability aligns with CWE-190, which specifically addresses integer overflow and underflow conditions, and represents a classic example of how improper handling of arithmetic operations in blockchain smart contracts can lead to severe financial consequences. The flaw operates at the core of the contract's state management system, where user balances are stored and modified, making it a fundamental weakness in the token's architecture that affects all users of the system.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it fundamentally compromises the trust and security model that Ethereum tokens are designed to maintain. An attacker with access to the contract owner account can arbitrarily set any user's balance to any value, including zeroing out balances, creating infinite balances, or transferring funds between accounts without authorization. This capability enables a range of malicious activities including account freezing, unauthorized wealth redistribution, and potential market manipulation that could devastate the token's value and user confidence. The vulnerability also creates a significant risk for the broader Ethereum ecosystem, as it demonstrates how poorly implemented smart contracts can serve as attack vectors that compromise not just individual tokens but also the overall integrity of blockchain-based financial systems. From an attacker's perspective, this vulnerability provides a direct path to financial gain through unauthorized balance manipulation, making it an attractive target for exploitation in the cryptocurrency space where such attacks can yield substantial returns.
Mitigation strategies for CVE-2018-13655 require immediate implementation of proper overflow protection mechanisms within the smart contract code, including the use of safe arithmetic libraries such as OpenZeppelin's SafeMath implementation that prevent overflow conditions through built-in checks. The contract owner must implement comprehensive input validation for all parameters passed to the mintToken function, ensuring that arithmetic operations remain within acceptable bounds and that user balances are properly constrained. Additionally, the implementation should include proper access control mechanisms to prevent unauthorized modification of user balances, and regular security audits should be conducted to identify similar vulnerabilities in other contract functions. The remediation process must also involve updating the contract's deployment procedures to incorporate automated testing for overflow conditions and formal verification techniques that can detect such vulnerabilities before deployment. Organizations should consider implementing multi-signature wallets for contract ownership to reduce the risk of single points of failure, and establish clear incident response protocols for addressing similar vulnerabilities that may be discovered in the future. This vulnerability also highlights the importance of adhering to established security frameworks such as the Ethereum Smart Contract Security Best Practices and following the ATT&CK framework's approach to identifying and mitigating smart contract-based attacks, particularly those involving state manipulation and privilege escalation.